To represent faulty reflecting elements, we multiply each reflecting coefficient by a failure mask \(m_n \in \mathbb {C}, n=1, \cdots N\)  [1]}, [2]}, which is defined as
\(m_n ={\left\lbrace \begin{array}{ll}1, & n\text{-th reflecting element is functioning} \\\eta _n e^{j\kappa _n}, & n\text{-th reflecting element is faulty}\end{array}\right.},\) 
